The surface contours of the linings of the subarachnoid space including the brain, spinal cord, nerve roots and nerve exits will be examined by scanning electron microscopy. This work will be supplemented by transmission electron microscopy of the same area combined with electron microscopic tracers. The objective will be to describe the surface structures lining the subarachnoid space and will include a "mapping" of the surface of the brain and the spinal cord insofar as regional differences may justify this procedure. Use of the scanning electron microscope will not necessarily be restricted to the above-mentioned area of the body nor will the work be restricted to the secondary electron mode of this instrument.